Conceptual Development of Sensing Module Applied to Autonomous Radiation Monitoring System for Marine Environment

We conceptually develop a scintillation-based sensing module for marine gamma-radiation monitoring deployed in an autonomous underwater glider to provide rapid responses to radiological emergencies. First, we replace the forward section of the glider with a robust YAlO3:Ce scintillator, and we analyze several streamlined scintillator configurations with different geometries via simulations of the mechanical and sensing performances. We calculate the minimum thickness required for the scintillator to remain operationally stable in deep ocean water for hemispherical and conical scintillator shapes. Next, we study the advantages and disadvantages of each shape in terms of the drag force and detection efficiency. After the background-radiation estimation of seawater, we calculate the minimum detectable activity (MDA) according to the counting time, which is a key factor in system operation. We find that all configurations can detect 137Cs within 30 min even at distances >600 km from a high-level-nuclear-accident site. Even in relatively minor instances, dozens of hours are sufficient for the optimized sensing module to satisfy a given MDA goal for 137Cs. Our results indicate that radioactivity data can be effectively mapped in 3D by autonomous motion of a monitoring system with the proposed sensing module.